Surface burner control



Feb. 21, 1939. C. A` PERSON v 2,148,407

SURFACE BURNER CONTROL Filed July 6. `1937 2 Sheets-Sheet l MVM mama n. zi, 1939 2,148,407

4uiu'n-:D STATES P.Al'ri-:N'rv ori-ics 2.148.407 amaca BUnNnoomoL om A. um Tampon'. non, by meme lldxnments, to Standard Electric Manufactnrlng Corporation, Toledo, Ohio, a corporation of h10 puceau my s, im, sum No. 15am 4 claim.. (ci. zie-s1) This invention relates to controls i'or electric be placed on the cover plate and will extract heating elements and is more particularly diheat therefrom in accordance with the relative rected to a control for surface burners ofthe type temperature of its contents and the temperature used in electric ranges. of the cover plate. Thus, if the contents o1' the The primary object ot the invention is the procooking vessel are relatively cold, considerable 5 vision oi' a sensitive means to control the current heat will be extracted from the-cove` plate and input to a surface burner to prevent overheating its temperature will be maintained relatively low ci' the burner and to hold its temperature at apso that the element 24 must supply considerable proximately a selected point. heat to raise the temperature of the cover plate. lo Another object of the invention is the pro- 'I'he cover plate is made relatively thin and of a ic vision of thermostatlcally operated means assomaterial which conducts heat readily so that it ciated with a surface burner in such a manner will give up its heat promptly to a cooking vessel that the current input to the burner is controlled placed thereon. Thecover Plate ShOuld be Suf= in accordance with the heat absorption characterciently thick however to discourage warping unistics of a body being heated by the burner. der repeated heating and cooling changes. 1

Other objects and advantages of the invention A heavy metallic conducting stem 26 depends will become apparent as the description proceeds, from the cover plate, and in the form shown in reference being had to the accompanying draw- Fig. 2, is integral therewith. In the form shown ings, in whichin Fig. 5, the stem is shown as separate from the Figure 1 is a`fragmentary plan view, with parts COVeI plate 25, and in this instance may be made broken away, of a burner and thermostat em- 0f a metal a Very high heat Cendllctivtifbodying @he invention; It will be obvious that the conducting stem 2@ Fig. 2 is a central vertical sectional view Will be heated t0 approximately the same temthereof; perature as the cover plate, since it conducts F1g 3 1s g, Section on une 3`3 of Fig. v2; heat very readily and, at least, will assume a tern Fig, 4 1S a View of the parts Shown in Fig, 3 perature always proportionate to the temperain another position; ture of the cover plate. The conducting stern Fig, 5 is a fragmentary section similar to Fig. 2 serves to mechanically reinforce the cover plate showing another form of connection between the so as to. prevent warping thereof. At its iower burner and the elements entering intothe present end, the conducting stern 26 is mechanically corfinvention; nected in intimate contact with a conductings Fig. 6 is a central vertical sectional view, with member 28 t0 which e IO 30 0f metal having a parts in full, of a modined i'orm of the invention; high heat conductivity is connected. A bimetal= Fig. 7 is a section on line l-'l of Fig. 6; lic thermostatic element 3i is coiled about the 35 Fig. 8 is a section on line 8 8 of Fig. 6; 30 so as to ne expanded by heat from the rod. .e Fig. 9 is a central vertical section, with parts pad of insulating material 3 insulator the ele- V in section, of another embodiment of the invenment 32 from any reflected or radiated heat which non; may emanate from the refractory cody 2&3. Fig. 10 ls a section on line lll-I0 of Fig. 9; and will be seen that the thennostatic element is er.:- 4@ Fig 11 1s a section on une of Fig, 10, posed to heat conducted from the cover plate 2 Referring to the drawings, the device is shown and hence Wil! Change its position in response to in connection with a stove top 20 in which a bowl a Change in the temperature conditions cfa cockmember 22 is disposed in the usual manner and. ing vessel supported thereby, as the relationship which, in the present instance, supports a refracbetween the temperatures of the cover plate and tory body 23 carrying an electric resistance elecooking vessel is such that they rise and fall toment 2d. Sather.

A thermostatic-circuit maker, shown in Figs. 3 At its outer end, the bi-metallic helix termin andA 4, is provided to control the current input to nates in a straight portion 36 which carries a conthe resistance 23 and may comprise any suitable tact 33. The straight terminal portion of the assembly of thermostatically actuated elements helix and its associated contact will be moved 5@ which are controlled by the heat of the resistance whenever the temperature of the bi-metal is element in the manner hereinafter described. A changed in response to a change in temperature metallic cover plate 25 is provided to overlie the o1 the cover plate. A conductor 40 runs between resistance element 24 and to be heated thereby. the contact 38 and a suitable binding post to In use, a cooking vessel or other receptacle will which the circuit connection may be made. The 55 of insulation 44 pivotally connected, as at 4B, to a small bracket 48 which is in turn carried by a plate of insulating material 58.

projects through the front panel of the stove 2g static switch g5 ator moves the The plate 58 is mounted for free rotary movement ony a Journal 52 associated with the rod 38 and is provided with a yoke 54 to which an operating stem 56 may be connected and which and terminates in a knob 68. It will be seen that as the knob 60 is turned, the plate 50 of insulating material will move and carry with it the adjustable contact 42. A conductor 62 connects the contact 42 with a suitable binding post carried on a sheet of insulating material 64 which also carries the binding post to which the conductor 40 is connected.

When the entire device is cold and the thermois in the o position, contact 38 Awill be separatedfrom contact 42. When it ls desired to use the burner, the thermostatic switch is moved to indicate the degree of temperature desired inthe burner and in so doing, the oper- .yoke 54 and plate 50 to bring contact 38 against contact 42 and'complete the burner circuit. As the temperature of the bimetallic helix increases, it will expand and uncoil so that contact 38 will slideon the adjustv able contact 42, the contacts being held together of the arm by a small tension spring 65. When the temperature reaches the predetermined, set point, the circuit will bebroken bythe contact 38 moving away from the contact 42, since the movement 44 which carries the adjustable' contact is limited by the small bracket 48. The point at which this circuit breaking will take place is shown in Fig. 3. vIn this iigure, further movement of the portion 36 of the bi-metallic element in a clockwise .direction will cause separation of the contacts and breaking of the circuit. In the form shown in Fig. 5, as above noted, the conducting stem 28 is made separate from the burner cover plate 25 and may be madeof any suitable metal having a high heat conductivity i1 the heat conductivity of the metal of which the cover 25 is made is deemed insumclent.

In the form shown in Fig. 6, the bi-metallic helix 10 is wound directly about the conducting .stem 26. An adjustable contact 12'is mounted for rectilinear movements relative to the contact 1l which is carried on the straight end portion ofthe bi-metallic element. The contact is connected to a. block 13 which is axially slidable in 55 a bracket 14 depending from'the burner assembly and is adapted to be moved by a stem 16 which carriesY a lug 18 received in a thread 80 formed on the interior of the block 13, whereby axial movement is imparted to the block when 80 the stem 16 is rotated.. Thus, the contacts may he given an initial setting to determine the nal temperature at which the movable contact 1I will move away from the adjustablel contact 12 and break the circuit to the resistance element 85 of the burner.

70 panslble chamber type 75 ducting stem 26 which depends from the burner cover. A suitable contact 94 may be operated by the chamber 80 and may be adapted to cooperate with an adjustable contact 96 carried on one end of an arm 88 connected to an adjusting rod N8, the arm 98 being similar in construction and operation to the arm 42 above described. It will be seen as the rod |06 is turned, the adjustable contact 88 will be moved toward or away from the contact 84 which is operated by the chamber 80. The advantage o! this modication 10 resides in the tact that a relatively long conduit 82 may be used to connect the conducting stem 26 with the chamber 88.

A11 of the modmcanons shown operate in the same manner so far as the circuit control is con- 15 cerned. Assuming that a cooking vessel or other body to be heated is placed over the burner plate, current will be permitted to enter the resistance element when the user sets the' knob 60 for the desired heat. This sets the adjustable contact 20 with relation to the contact carried by the thermostatically actuated element. As the resistance becomes hot, heat will be transferred to the cover plate 25 and a portion thereof will be conducted away through the conducting stem 26 and 25 its associated conducting elements, such as mem- Y ber 28 and rod 30 in Fig. 2. Thus, all of the parts will assume a temperature proportionate to the temperature of the cover plate. It the setting o! the knob 68 is such that the circuit contacts open 30 only under high temperature, as for example 400, the full heat will continue to flow into the f cover plate until this point is-reached. If the cooking vessel contains cold water, it will absorb heat from the cover plate and prevent this lat- 35 ter from reaching the set temperature until the contents of the cooking vessel have absorbed suilicient heat so that the rate of absorption has decreased, as for example, when water contained in the vessel has reached its boiling point. As the rate of heat transfer to the cooking Vessel decreases, the conducting stem and hence the remaining conducting parts will increase in temperature and move the thermostatically operated contact away from the adjustable contact to openf the resistance circuit. It has been round that a device of this character is very sensitive to heat conditions of the cooking vessel.

It will be noted that by reason ofthe pad of insulating material 34 placedbetween the refractory in which the heating resistance is seated, heat transfer by radiation from the refractory to the bi-metallic element is prevented and the latter responds only to heat conducted away from the cover plate.

While the invention has been disclosed in connection with several modications, it will be appreciated that other changes may be made in the form and disposition of the parts without departing from the spirit of the invention as de- 'fined in the appended claims.

What I claim is:

l. In a surface burner for electric stoves, an electric heating element having a switch in circuit therewith, a metallic cover plate overlying said heating element and being comparatively thin to render it quickly sensitive to temperature conditions of a cookingvessel placed thereon, electric and heat insulating means disposed below said heating element, a metallicstem having rapid temperature conducting connection with said plate and having a cross sectional area suitable for rapid conductionof heat from the plate, said stem lextending down through said insulating means, and thermostatic means connected to said stem at the opposite side of said insulating means to said plate and operable by predetermined temperature changes in the stern in response to temperature changes in said cooking vessel to open and close said switch.

2. In a surface burner for an electric stove, an electric heating element having a switch in circuit therewith, a metallic covery plate overlying said heating element and being comparatively thin so that it is highly sensitive to temperature changes of a cooking vessel placed thereon, electric and heat insulating means at the opposite side of said element to said cover plate, a metallic conductor extending downward from the cover plate through said insulating means, and thermostatic means connected to said conductor and operable by predetermined temperature changes in the conductor to open and close said switch, said conductor being of a cross sectional area suitable for rapid conduction of heat from said cover plate whereby the relative temperature of said cooking vessel in contact with the cover plate is rapidly communicated to the thermostatic means.

3. In a surface burner for electric stoves, an electric heating element, a metallic cover plate overlying said element and being of thin nature to render it quickly sensitive to temperature changes of a cooking vessel placed thereon, a metallic heat conductor extending downwardly from said cover plate, electric and heat insulating means disposed below said heating element and surrounding said conductor, a switch in circuit with said heating element, and thermostatic means connected to said conductor and operable by predetermined temperature changes in the conductor in response to temperature changes in said cooking vessel to open and close said switch. 4. In a surface burner for electric stoves, an electric heating element, a metallic cover plate overlying said element and being of a thin nature to render it quickly sensitive to temperature conditions of a cooking vessel placed thereon, an electric insulating element below said resistanceI element, a heat conductor connected lnteriorly to said plate and extending downwardly through said heating element, an electric switch in circuit Witlr said resistance element, and thermostatic means connected to said conductor and operable by predetermined temperature changes in the conductor in response to temperature changes in the cooking vessel to open and close said switch.

CHARLES A. PERSON. 

